This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. MRI Assessment of Pallidotomy Lesion Placement and Post-operative Localization in Parkinson's Disease In recent years, the use of radiofrequency ventroposterior pallidotomy (VPP) as a symptomatic treatment for the medically refractory motor symptoms of Parkinson[unreadable]s disease (PD) has been gaining widespread acceptance. A number of centers have reported significant improvements in controlling disabling dyskinesias, on/off fluctuations and other motor symptoms in patients with idiopathic PD (Baron et al., 1996;Dogali et al., 1995;Iacono et al., 1995;Johansson et al., 1997;Lang et al., 1997;Laitinen et al., 1992a;Laitinen et al., 1992b;Lozano et al., 1995;Uitti et al., 1997). Although there is a general agreement that VPP is helpful for many patients, results vary considerably between patients and centers performing the operation. One reason for this variability is likely due to differences in lesion placement and size.